Communication system



June 13, 1939. R. H. CAMPBELL COMMUNICATION SYSTEM Filed July '19, 1937 A further object of the invention is to pro-- Patented June 13, 1939 PATENT OFFICE COMMUNICATION SYSTEM Richard H. Campbell, Racine, Wia, minor to Webster Electric Company, Racine, Win, a corporation of Wisconsin Application July 19, 1937, Serial No. 154,345

13 Claims.

The present invention relates to intercommunication systems, and particularly to systems comprising a single central or master station and one or more remote stations.

v It is an object of this invention to provide an intercommunication system with an improved arrangement for producing a signal at the central station whenever an operator at a remote station desires to communicate with the central station.

A further object of the invention is to provide an intercommunication system with signaling means enabling an operator at the central station to determine at a glance which of the remote stations desires to communicate with the central station, and in which certain interstation conductors are used both for transmission of speech and for actuating the signaling means.

A further object of the invention is to provide a multiple station intercommunication system with signaling means including a single audible signal and a plurality of visual signals, the audible signal being actuable from all remote stations and a predetermined one of the visual signals being actuable from any particular remote station.

vide a communication system of the type described in which both the audible and visual signals are actuated through the same interstation conductors.

A further object of the invention is to provide a multiple station intercommunication system comprising direct current speech transmitting means and alternating current signal actuating means, in wh ch common conductors are utilized in a non-interfering manner for transmitting speech and actuating the signals.

Other objects and advantages of the present invention will become apparent from the ensuing description, in the course of which reference .is had to the accompanying drawing, the single figure of wh ch is a schematic circuit diagram of one embodiment of the invention.

Referring now ro the drawing. the reference numeral I0 designates voice receiving and transmitting means, such as a dynamic loudspeaker of the type employing a permanent magnet and a voice coil suspended in the field thereof, located at a station from which the communication systemis to be controlled. This station may be aptly,

termed either a master or central station, and

hereinafter will be referred to as a central stabetween which and the control sired to communicate. v

The fluctuations in current produced in speaker units when acting as transmitters are amplified by an amplifier l2 oi. any suitable type comprising one or more stages of amplification and supplied with power from an alternating current source through a rectifier. The amplifier may be provided with volume control as well as a switch for connecting it to a suitable source of power, but since these elements, as well as the amplifier itself, may be of any well known construction, they are not illustrated -or described in great detail herein. For present purposes, it is deemed suflistation it is decient to state that the amplifier comprises input 15 and output transformer coils l3 and M, respectively, each having one terminal thereof connected to a common conductor l5 which is grounded as indicated at I6. I

A selectively operable master switch I! is pro- 20 vided at the central station for connecting the speaker unit It) thereat to either the output or input of the amplifier, and simultaneously conditioning the remote speaker units II for connection to the input or output of the amplifier, 25

through selector switches I 8, also located at the central station and corresponding in number to the number of remote stations.

' The selector switches l8 not only serve the purpose of connecting the remote stations to 30 the master switch I], but also provide means adapted to cooperate with control switches l9 at the remote stations for actuating an audible signal, such as a buzzer 20, and visual signals 20' at the central station. The signal actuating circuits are so arranged that whenever an operator at a remote station wishes to communicate with the central station, he displaces the switch I9 from its normal position to a displaced position thereby to actuate the buzzer 20 and the visual signal means 20 associated with that station. The details of this circuit arrangement are described hereinafter.

The master switch I! is biased by suitable' means, such as a spring, to a normal position in which the speaker unit I 0 is connected to the output coil l4 and the speaker units l I are conditioned for connection to the input of the amplifier by means of the selector switch l8. Switch I1 is a double pole double throw switch connected for operation as a reversing switch. The switch blades 2| and 22 thereof are connected by conductors 23 and 2| to the voice coil of speaker unit I 0 and to a plurality of branch conductors 25,

lector switches it are also double pole double throw switches, the other blades 21 0'! which are normally closed switches connected by conductor 2! to the common conductor ll,

Returning now to the construction of the reversing switch and its circuit connections, it may be noted that the ungrounded terminal of the input coil I3 is connectedby a conductor II to the interconnected contacts 32 and 28 01' the switch, and that the output coil i4 is similarly connected by a conductor 34 to the interconnected contacts I! and II.

In the normal position of the master switch 11 the voice coil associated with speaker unit I0 is connected across the output of the amp'lifler through conductor 24, switch blade 22 in engagement with contact 25, and conductor 23 leading to one terminal of the voice coil, the other terminal of which is connected by a conductor 21 to the common conductor I. ,In the displaced position of the switch, the voice coil is connected across the input of the amplifier through conductor 3!, switch blades 22 in engagement with contact I2, and conductor 23 and through the conductor 31.

The selector switches I. are biased into a nor mal position in which the system is conditioned for the actuation of the audible and visual signal means at the central station from any one of the remote stations. In this position the switch blades 26 thereof are in circuit opening position and the switch blades 21 are in engagement with contacts 4|. The 001. acts 4| are connected by conductors 42 to low impedance solenoid windlugs 43 adapted when energized to actuate the visual signals into positions in which they may be observed by the operator at the central station. The visual signals may conveniently consist of an armature 44 that must be manually returned to a normal position in .which the signal is not in view. Thus, whenever the winding 42 is energized, the signal 20' is brought into view and remains there until the operator at the central station returns it to its normal position. The solenoid windings 43 are connected by conductors 45 to interstation conductors 46 leading to the switch blades 41 of the control switches Id at the various remote stations. Conductors 48 are also connected to contacts 48 adapted to be engaged by switch blades 26 of the selector switches l8 in their displaced'position.

The switch blades 41 of the control switches are adapted normally to establish circuits from conductors 46 to conductors 49 connected to the terminals of the voice coils of the remote speaker units, the other terminals of which are connected by a common conductor 50 to the common conductor IS.

The switch blades 41 are operable to a diuplaced position in which they engage contacts 5| connected by a conductor 52 to the buzzer 20. The other terminal of the buzzer is connected to the low voltage secondary winding of a transformer 53, the primary winding of which is connected to any suitable source of alternating current power which'may be and preferably is the source supplying power to the amplifierrThe other terminal of the secondary winding of the transformer is connected by aconductor 54 to the common conductor ii.

In operation, the amplifier i2 is supplied with power from any suitable source and is normally in an operative condition so that speech may be transmitted from the central station to the remote stations or vice versa at all times. Likewise, the transformer 53 is connected to a suitable source of power to provide a source of low voltage for the signal actuating portion or the system.

The system is normally conditioned for actuation oi the signal means at the central station from any one of the remote stations by reason of the fact that the selector switches ii at the central station are biased into a position in which the switch blade 20 is in circuit breaking position and the blade 21 connects the relay winding 42 to one side of the secondary winding of transformer 53 through conductors 28 and it. Thus whenever the operator at a remote station desires to communicate with the master station it is only necessary for him to operate the switch blade 41 from its normal to its displaced position wherein it engages contact ii to complete a circuit through the relay winding and buzzer. The circuit is completed through conductors 45, 4, switch blade 41, in engagement with contact 5|, conductor 52, to the buzzer 20 and thence directly to the terminal of the secondary winding. Thereupon the buzzer 20 gives an audible signal and the relay winding 42 actuates its armature 44 to position the visual signal means associated therewith so that it can be observed by the operator at the central station.

The audible signal apprises the operator at the central station that one of the remote stations is calling and the visual signal apprises him of the particular remote station calling. Thus the necessity of the operator remaining at his post at all times is avoided.

If the operator at the central station wishes to respond to the call, he operates the selector switch i8, corresponding to the station calling, into its displaced position in which the switch blade 26 thereof is in engagement with contact 48 and the switch blade 21 in its open position. The opening of switch blade 21 disrupts the signal circuit from the selected remote station and the closure of switch 28 establishes a circuit from the speaker unit at the selected remote station to the input of the amplifier through the switches 4'! and H in their normal positions. The circuit extends from the input coil of the amplifier to the voice coil of the remote speaker H through conductor 3|, switch blade 2| in engagement with contact 33, conductor 24, branch conductor 25, switch blade in engagement with contact 46, conductor 46, and switch blade ll in engage ment with conductor 49.

At this time the speaker unit iii at the central station is connected across the output coil of the amplifier through a circuit that has been described previously and which includes conductor 34 and the switch blade 22 in engagement with contact 35.

When the operator at the central station wishes to talk to the operator at the remote station selected, he :lmply operates the master switch H to its displaced position at which time the speaker unit at the central station is connected to the input coil of the amplifier and the speaker unit II at the remote station to the output coil of the amplifier.

When the conversation is completed the operator at the central station simply releases the master switch [1 and the selector switch l8, thereby conditioning the system for actuation of the signal means at the remote station ii whenever the operator at the latter station desires to communicate with the central station.

In view of thefact that each of the remote stations has its own visual signal means and selector switch at the central station, an operator at the remote station may indicate a desire to communicate with the central station while the central station is in communication with another of. the remote stations. Furthermore, since the switch blades 26 of the various selector switches l8 are in parallel, the central station can be placed in communication with all the remote stations simultaneously by manipulation of the selector switches into their displaced positions.

The system described above is adapted for use with any number of remote stations and it should be apparent to those skilled in the art that the selector switch l8 need not be one which is biased into a predetermined position. Its operation may be controlled entirely by the operator at the central station. In the event that it is not biased to a predetermined position. it should be .manually returned to its normal position upon completion of a conversation.

The system is adapted particularly for use in locations where it is not convenient for an operator to be stationed at the central station at all times. An example ofthis type .of use is furnished by tool rooms or warehouses in which thereis only a single attendant. The attendant may leave the location of the speaker unit and if any one calls him in his absence, he is apprised of the fact by the visual signal means, as well as by the audible signal.

Another advantage of the system resides in the fact that it may be operated from a single source of alternating current power because there is no interference between the direct current communication system and the alternating current signal actuating circuit. Interference is eliminated by disrupting the signal circuit whenever communication is established by operation of switch blades and 21.

While only a single embodiment of the invention has been described, it is not contemplated that the principles of the invention should be limited thereto. Other modifications thereof will suggest themselves to those skilled in the art and it is contemplated that the present invention is limited only by the claims appended hereto.

What I claim as new and wish to secure by United States Letters Patent is:

1. In an intercommunication system, the combination including a pair of remotely located stations, means including plural position switches at one station for controlling a communication circuit and a signal circuit between the two stations, said switches being operable to a position in which the communication circuit is open and the signal circuit conditioned for closure,

and means including a control switch at the other station normally closing the communication circuit thereat and operable to a displaced position for completing said signal circuit.

2. In an intercommunication system, the combination including a pair of remotely located stations, voice receiving and transmitting means at each station, means including plural position switches at one station for controlling communication and signal circuits between the two stations, said switches normally occupying positions in which the communication circuit is open and the signal circuit closed, and means including a" switch normally connecting the voice receiving and transmittingmeans at the other station to the communication circuit for completing the munication and signal circuits, a control switch at the other station for controlling said circuits, said first mentioned switch being operable to a predetermined position to disconnect the voice receiving and transmitting means at said station from said conductor and to connect the signal means-thereto, and said control switch normally completing a connection from an interstation conductor to the voice receiving and transmitting means at said other station and operable to com-- plete a signal actuating circuit through said first mentioned switch when the latter is in said predetermined position.

4. In an intercommunicating system, the combination including a pair of remotely located stations, speech receiving and transmitting means at each station, sign'al means at one station, means including an interstation conductor and a pair of simultaneously operable switches at said one station for controlling communication and signal circuits extending in part through said conductor, a control switch at the other station for additionally controlling said circuits, said first mentioned switches being biased into a normal position in which one of said pair of switches opens the connection of the communication circuit to the interstation conductor and the other closes the signal circuit and operable into a displaced position to complete the communication circuit and open the signal circuit, and said control switch being biased into a normal position to complete the connection of the voice receiving and transmitting means to the interstation conductor and operable to a displaced position to complete the signal circuit, whereby the system is conditioned for actuation of the signal means at the central station upon operation of said control switch to its displaced position and for transmission of speech upon operation of said first mentioned switch to its displaced position.

5. In an intercommunication system, the combination including, a central station, a plurality of remote stations, means including a number of plural position selector switches at the central station equal to the number of remote stations for controlling communication and signal circuits between the central station and the remote stations, said switches being operable to a position in which the communication circuit is open and the signal circuit conditioned for closure, and means including control switches normally closing communication circuits at the remote stations for completing the signal circuit through the selector switchassociated with that station.

6. In .an intercommunication system, the combination including, a central station, a plurality of remote stations, voice receiving and transmitting means at each station, an audible signal and a number of visual signals equal to the number of remote stations at the central station, means including a number of plural position selector switches equal to the number of remote stations at the central station for controlling communication and signal circuits between the central station and the remote stations, said switches being operable to a position in which the-cominunication circuits to the associated remote station are open and.the circuits to the audible signal and visual signals are conditioned for closure, and means including a control switch at each remote station normally connecting the voice receiving and transmitting means at that station to the communication circuit for completing the circuit to the audible signal and the visual signal as-.

'sociated with that station.

'7. In an intercommunication system, the com bination including, a central station, a plurality of remote stations, loudspeaker units at each station, signal means at the central station, means including a number of interstation conductors and a similar number of double pole switches at the central station for controlling communication and signal circuits extending in part through said conductors, a control switch at each remote station for additionally controlling said circuits, said first mentioned switches being biased to a normal position in which one blade of each of said double pole switches opens the connection of thecommunication circuit to the interstation conductor and the other closes the signal circuit and operable to a displaced position to complete the communication circuit and open the signal circuit, and said control switches being biased into a normal positionto complete the connection of the loudspeaker units to said interstation conductor and operable to a displaced position to complete.

the signal circuit, whereby the system is conditioned-for actuation of the signal means at the central station upon operation of any one of said control switches to its displaced. position and for communication to the remote station upon operation of any one of the double pole switches to its displaced position.

8. In an intercommunication system, the combination including, a central station, a plurality of remote stations, loudspeaker units at each station, an audible signal and a number of visual signals equal to the number of remote stations at the central station, said signals being electrically actuable and connected in series parallel relationship whereby the audible signal is actuated whenever any one of the visual signals is actuated, means including a number of double pole switches and interstation conductors equal to the number of remote stations at the central station for controlling communication and signal circuits extending in part through said conductors, a control switch at each remote station for additionally controlling the communication and signal circuits, said first mentioned switches being biased to a normal position in which one blade of each opens the connection of the communication circuit'to the interstation conductor and the other closes the parallel branch circuit including the visual signal and operable to close the communication circuit and open the'signal circuit, and said control switches being biased into a normal position to, complete the connection of the loudspeaker units at the remote stations to said interstation conductor and operable to a displaced position to complete the connection of the signal circuit through the audible signal and the associated visual signal to a source or power.

9. In an intercommunication system, the combination including, a pair of remotely located stations, loudspeaker units at each station, an amplifier, a double pole double throw switch at a first station for connecting the speaker unit at that station to the output and input of the ampliiier and simultaneously connecting a communication circuit extending to the second station to the input and output of the amplifier, said communication circuit including a normally ..open

switch at the first station and a normally closed switch at the second station, signal means at the central station, and means including a normally closed switch operable simultaneously with said normally open switch and a circuit adapted to be closed by the normally closed switch at the second station in its communication-circuit opening position for actuating said signal means.

10. In an intercommunication system, the comblnation including, a central station, a plurality or remote stations, loudspeaker units at each station, an amplifier, a double pole double throw switch at the central station for connecting the speaker unit at that station to the output and input of the amplifier and simultaneously connecting a communication circuit to the remote stations to the input and output of the amplifier, said communication circuit comprising a common conductor and a branch interstation circuit leading therefrom to each remote station, each 01 said interstation circuits comprising a normally open switch at the central station and a normally closed two position control switch at the remote station, signal means at the central station, and

means including a switch at the central station operable conjointly with the last mentioned switch at the central station and cooperating with the control switch at the remote station in its other position for'actuati'ng said signal means.

11. A multiple station intercommunication system, including in combination, a central station, a plurality of remote stations. a loudspeaker at each station, an amplifier, signal means at the central station, means for selectively connecting the loudspeaker thereat to the output and input of the amplifier and simultaneously connecting the loudspeakers at the remote stations to the input and output of the amplifier, said means including a reversing switch and a selector switch for each remote station located at the central station, and a control switch located at each remote station, said selector switches normally breaking a circuit from the reversing switch to the control switch associated therewith, and said control switch normally completing a circuit from its associated selector switch to the speaker, and means for actuating said signal means from all said remote stations, said means including a plurality of parallel circuits adapted to be completed through a selector switch in its normal position and a control switch in its displaced position.

12. An inter-communication system, including in combination, a central station, a plurality of remote stations, loudspeakers at each station, an amplifier having input and output terminals, a

master switch at the central station for connecting the speaker thereat to the output and input and simultaneously conditioning the speakers at the remote stations for connection to the input and output of said amplifier, said switch being biased to connect the speaker at thecentral station to the output and to condition the remote speakers for connection to the input of the amplifier, a plurality of selector switches at the central station operable from a normal position to a second position for selectively completing the connection of the respective speakers at the remote stations to said master switch, said last mentioned switches being biased to-their normal positions, a

a switch at each remote station normally connect ing the speakerthereat to the second position of 

